Concentration of NH3(aq) Required for Incipient NH3 Toxicity to Seedlings1
- A. C. Bennett and
- Fred Adams2
Short term experiments with sudangrass (Sorghum sudanensis L.) and cotton (Gossypium hirsutum L.) were conducted in a growth chamber to determine incipient toxic levels of NH3(aq). Sudangrass seedlings were grown for 14 days in potted Lucedale sandy loam surface soil treated with different rates of N from NH4OH, (NH4)2SO4, and (NH4)2HPO4. Root growth of cotton seedlings was measured over a 3-day period in split-root experiments in which the upper portion of the root medium was a sandy loam surface soil and the lower portion was either a nutrient solution or a treated soil at various levels of pH and ammoniacal-N. Symptoms of NH3 toxicity were evident on sudangrass foliage at NH3(aq) concentration in the soil solution in situ of 0.17mM and greater; there was no evidence of NH3 toxicity at 0.13mM and less. Symptoms of NH3 toxicity on cotton roots were evident in soil solutions in situ at NH3(aq) concentrations of 0.24mM and greater but not at 0.17mM and less; in nutrient solutions, symptoms were evident at 0.22mM NH3(aq) but not at 0.16mM. The critical concentration for incipient NH3 toxicity was concluded to be 0.15 to 0.20mM NH3(aq).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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